JPS61191087A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To obtain a distributed feedback type semiconductor laser, wherein leak currents are few even when a large current is injected and high speed modulation is possible, by using Fe added high-resistance InP as an embedded layer for narrowing a current. CONSTITUTION:On an n<+>-InP substrate 21, a diffraction grating 23 is formed. Then non-added InGaAsP 22 is grown on the diffraction grating 23. An Fe- added, high-resistance InP layer 30 is grown on the layer 22. An SiO2 film 27, in which a stripe shaped window (groove) 31 is patterned, is provided. The Fe-added, high-resistance InP 30 is selectively etched. Then the n-InGaAsP layer 22 is selectively etched. In this process, the diffraction grating 23 appears at the bottom of the groove. Then, an n-InGaAsP guide layer 24, a non-added InGaAsP active layer 25, a p-InP layer 26 and p-InGaAsP layer 33 are sequentially grown. Finally, an SiO2 film 32 having a stripe shaped window is deposited. Ti/Pt/Au is formed as a p-type electrode 28 on the film 32, and AuSn is formed as an n-type electrode 29 on the back surface of the substrate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor light emitting device C2, a special C low threshold current,
The present invention relates to a distributed feedback semiconductor laser device C2 capable of high output, high efficiency, and high speed modulation.

[Conventional technology]

Currently, as a radar that oscillates in a single longitudinal mode even during high-speed modulation of several hundred megabits/second to several gigabits/second, the distributed feedback type (j) istribut*dp@a
dbaek; DFB) lasers are the mainstream. Conventional DFB radars include the main types of DFB radars shown in FIGS. 4 to 6.

Figure 4 shows a $1 example of a conventional DFB laser (embedded type,
BH,' Buried H@t＊rostructu
r*), and the upper C binomial ζ2n of the n-InP substrate 1
-InGaAsP guide) m2, InGaAsp
Active layer 5. A p-InP upper cladding layer 4 and a p-InGaAsP layer 8 as a cap layer are formed in an i-formed structure. and,
Active layer 34 from reverse mena structure C2! : The width of each growth layer included is defined, and both sides of the inverted mesa structure Cp-InPj-
6 and n-InP layer 7 are buried. Sara C dioxide film (
A p-type electrode 9 is provided through seven of the openings 10.

During operation, p-InP layer 4, n-InP layer 7,
The p-n-p-n structure formed from the p-InP substrate 1 and the n+-InP substrate 1 prevents the C2 current indicated by the solid arrow from leaking, and magnetic current confinement is performed.

However, when a large current is passed through the p-re layer 4 to the p-InP layer 6, a leakage current as shown by the broken line arrow occurs, which triggers the p-n-p-n. As a result of the conduction of the Nyristor structure, there is a drawback that current confinement becomes insufficient. Furthermore, as shown in FIG. 4, there is also the drawback that the semiconductor surface is not flat.

Figure 5 shows a second conventional example (flat embedded type, PBH;
Munsr Burled Heteroatructu
re), and is numbered C2 so as to correspond to each part in FIG. 4, and if there are two parts C2 with the same number, C2 is essentially the same as in FIG. 4.

The feature of this example is that a p-InP layer 11 is provided to planarize the surface of the semiconductor element. However, the problem of insufficient current confinement cannot be improved.

1g6 diagram is D C-P BH (Doubts Chax
uxstPmu nor Buried) fsterost
4 and 5, and the numbers are the same as in FIGS. 4 and 5. In this third conventional example, active layer 34I: grooves 12° to 13° are dug on both sides of the active layer 34I, including p-InP layer 6 and n-InP@7t'.
Point to embed.

and below the embedded layers (6, 7) on its side (24-element layer (I
It is characterized by the presence of an nGaAsP layer 6).

This quaternary layer creates an emitter as shown in Figure 6C.

The gain of the transistor structure with ■ as the pace and ■ as the collector decreases, and as a result, the leakage current (in this case, from p-InP4 in the upper cladding layer to p-InP4 in the buried layer) decreases.
This is an attempt to solve the problem in which the p-n-p-n constriction mechanism becomes insufficient due to the leakage of current.

[Problem that the invention seeks to solve]

The common drawbacks of the above conventional semiconductor radars are that (D current blocking layer (= p-n-p-n junction) is used, so when high current is injected, complete current blocking cannot be achieved.
(1) Sufficient high-speed modulation cannot be achieved due to the capacitance caused by C2 such as the p-n junction of the current blocking layer. (2) After the active layer grows (;
This is because the active layer is likely to be thermally damaged because the second and third growth steps are required.

[Means for solving problems]

The present invention solves the above problems by using a current blocking layer CFe (iron) f: added high resistance InP.

The structure of the present invention will be explained by referring to the embodiment of the present invention shown in FIG.
After forming a high-resistance layer of Fe-doped 1nP layer 301 on top, and forming #31 in the form of selectively etched C-niel stripes, C2-activated J@25 etc. are grown during the second growth.

[Function] If the refined I of the present invention is used, the high-resistance I added with F@f
Since the current collector layer is formed using nP/jig, leakage current can be reduced, and capacitance due to the current blocking layer can be reduced, resulting in high-speed modulation.

In the present invention, the InP Jt high-resistance layer doped with Fe has a high resistance with good reproducibility; resistivity t5
”It is clear that Ω・minor level or higher can be obtained6
Second, it is for ivy. When Fe is added to InPl2, it acts as a deep level impurity and a stable high resistance layer is obtained. On the other hand, other impurities that are thought to create a deep level, such as Co (cobalt), do not provide a stable high resistance. Also Nl
Nickel) has the disadvantage of impairing the crystallinity of InP. It is also possible to add a relatively shallow level of impurities such as Cd, Zn, Mn, etc., but it is difficult to control, a p-type layer is likely to be formed, and a high-resistance layer cannot be obtained with good reproducibility.

Next, if the present invention (:J:) is used, the second growth (::Grows on the active layer, so the number of heat treatments after forming the active layer is reduced compared to the conventional method, and thermal damage to the active layer is reduced. Benefits arise.

〔Example〕

The following will explain the embodiments of the present invention shown in FIGS. 1 and 2.

Refer to Prisoner 21■ First, (100) n+-InP group vjL21, interference exposure and chemical etching C Nyeri, Pit Y-397
A diffraction grating 231 of 0x and depth of 1000 is formed.

Figure 2 (Bl 0th order, C2 on the diffraction grating 23, undoped (undopsd)
) InGaAaP (λ, , = t, 1s l1m')
224r: Approximately 0.2μ, high resistance I with addition of C2Fe
nP #50 t' grows to about 2 μm. This growth is LP
E (liquid phase growth method) or MOC'VD (chemical deposition method using organometallic raw material gas) is used.

The growth temperature is approximately 70°C to increase the solubility of Fa in In.
The temperature shall be 0°C. Due to the high temperature growth, there is a concern about thermal deformation of the diffraction grating 23, so the GaAs wafer is not used until the start of growth.
It is best to cover the surface of the InP substrate by using a QaAs wafer (good results have been obtained from experience using a QaAs wafer). LPE
(:), the composition of the Fe-added InP melt is In
: P: Fe = 1 g: 20 mg: 15 mg.

Refer to FIG. 2(C), 810 film 27f patterned with a striped window (groove) 51 having a width of 3 μm: Provided, HCL: Ha
The Fe-added high resistance InP layer 30 is selectively etched with PO number: 3:1, and then Ha 304 : Hoot : H
The n-InGaAsP layer 22 is selectively etched at a ratio of 0=90:5:5. During this process, a diffraction grating 23 appears at the bottom of the groove.

Figure 2 (see trout ■ n-InGaAsP (22% = t1s μm) guide layer 24. Additive-free InGaAaP active layer (λ- = 1.5
μm) 2S, p-InP cladding layer 26. and p
- The InGaAsP cap layer 33 is sequentially grown. The growth starting temperature is 600°C (LPE). The carrier concentration and film thickness of each layer are calculated as follows: 1 carrier concentration (n or p
) Film 4 (d) n-InGaAaP layer p n
= 5 x 10"tM-', d = 0.1μ
m (Guide III) (Sn addition) InGaAiP active layer* n-1X 10”c
rR-”, d=o, 15/Jm (no additives) p-InP cladding layer s P=5X101?3-
”, d=2μm (Ca addition) p(nGaAsP cap layer: II=4×10”m
-', d==o, 2/Jm Note that the cooling rate during multilayer growth is about 17° C. per minute.

(The end (= 2 widths of 5ils with a striped window)
1 film 32 is deposited, Ti/Pt/Au is deposited on top of it as a C2p-type conductor f4i28, and an n-type conductor J429 is deposited on the back side of the substrate.
As a result, Au8nt' is formed.

■Resonator length 4t! In order to suppress Fabry-Perot mode oscillation, the cleavage ends 1i1i4 are cleaved to 150 μm.
1: By coating with Si, N, film (antireflection film), the distributed feedback semiconductor laser shown in FIG. 1 is completed.

FIG. 3 shows another embodiment of the invention.

In the previous figure 'S2, the pq electrode 2B is located on the upper part of the 5ICh film 62 with a striped window located on the active layer 25.
However, in that structure, the stripe external C two metal/insulator/semiconductor structure is formed over the entire dii
il = exists across C2. Therefore, it is conceivable that the parasitic capacitance adversely affects the high-speed modulation characteristic C2. Therefore, the embodiment shown in FIG. 6 is an attempt to improve this. After the filling growth of the first part of the active layer 25 is completed, a striped SiO2 film with a width of 50 μm is formed at a position corresponding to the upper part 62 of the active layer 25 ( (not shown) 4r: deposited;
Using this mask C2, remove bromine/methanol = α2.
, p-type 1nP clad II 26 , InGaAs
P active layer 25, n-InGaAmP guide layer 24
, Fe-doped InP current blocking layer (high resistance InP layer) 30
is removed to a total depth of about 1.5 μm.

After that, the StO film (not shown) was removed, and the p-InG
On the aAiP cap layer 33, Ti/Pt/Au t' stripes are formed as the p-type XE electrode 28.

In this example (:J:, from the reduction of parasitic capacitance C2, the
; Good high-speed modulation characteristics can be obtained.

〔Effect of the invention〕

In the present invention, from the above-mentioned Fe-doped high resistance InP4 lumped J- for current confinement C2, current leakage is small even when high current is injected ≦2, and high-speed modulation is possible. A feedback semiconductor radar is provided. In addition, there is an advantage in manufacturing that there is less thermal damage to the active layer during growth.

[Brief explanation of drawings]

Figure 1 is a perspective view of an embodiment of the present invention; Figures 2 (4) to (trout are manufacturing process diagrams of an embodiment of the present invention;
FIG. 5 is a sectional view of another embodiment of the present invention, and FIGS. 4 to 6 are respectively conventional distributed feedback semiconductor lasers.
The figure is a recessed type, FIG. 5 is a flat recessed type, and FIG. 6 is a sectional view of the main part of a flat recessed type with a double channel. Main code 21...♂-1nP substrate 22 = (no additive) InGaAsP24- n-I
nGaAsP (Guide a>25 (no additives) In
GaAsP (active layer) 26-=p-InP (cladding #) 28...p-type electrode 29...n-type electrode

Claims (1)

[Claims] Fe-doped high resistance I on InP substrate with diffraction grating
an nP current blocking layer; a groove formed in the current blocking layer;
A semiconductor light emitting device comprising a guide layer, an active layer, and a cladding layer, which are sequentially embedded in the groove.